Electric current rectifier



March 3, 1936. s RUBEN ELECTRIC CURRENT RECTIFIER Filed April l5, 1955INVENTOR g ONEY ATT SESS

Patented Mar. 3, 1936 UNITED STATES PATENT OFFICE ELECTRIC CURRENTBECTIFIER Application April 13, i933, Serial No. 665,869

9 Claims.

This invention relates to electric current rectiers and the like whichemploy asymmetric or unilateral conductive couples of the drysurfacecontact variety, the term "unilateral conductive couple as usedhereinafter being intended to designate a device including an electrodeelement of a relatively electropositive material and another electrodeelement of a relatively electronegative material adapted to cooperatewith the 10 former for the y electrochemical formation and maintenanceat their junction of an inverse current-blocking nlm which has theproperty of conducting current in one direction and blocking current inthe reverse direction.

General objects of the invention are the provision of such coupleshaving improved characteristics, which are eiliclent, economical andreadily manufactured, and have long service lives; the provision of anadditional element in such couples which tends to prevent inoperation'the formation of polarizing material of a character whichreduces the emciency and shortens the service life; and structuralembodiments of the device which are readily constructed and alloweiiicient use and operation thereof.

A specific object f the invention is the provision of such a coupleprovided with a layer of non-polarizing substance in contact with thematerial constituting the electronegative electrode element thereof toprevent the formation in operation of polarizing material adjacent theelectronegative material, and to insure steadiness of output andincreased eiliciency.

Anotherobject of the invention is the pro- 5 vision of such a unilateralconductive couple wherein the electropositive electrode element iscomposed of a relatively electropositive material formed from one of theelements chosen from an empirical group including beryllium, magnesiu 10calcium, zinc and aluminum, or alloys or compounds thereof, and theother electrode element is composed of a relatively electronegativematerial, preferably including at least one compound of at least one ofthe elements sulphur, selenium,

5 and tellurium, the couple additionally being characterizaed by a layerof a non-polarizing substance interposed between the electronegativematerial and a terminal member.

A further object of the invention is the pro- .zo vision in such aunilateral conductive couple having an electropositive electrode of asilicon material having a high contact resistance with theelectronegative electrode element and preferably formed from a silicidecompound of 55 one of the elements chosen from an empirical Cal (Cl.F15-366) the elements sulphur, selenium and tellurium, of a 5 weldedjunction obtained by subjecting the electropositive and electronegativematerials to a iiow of electric current to weld them together to form aphysically and electrochemically stable unitary couple element.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises' the features of construction,combination of elements and arrangement of parts which will be exempli-15 lied in the following detailed disclosure, and the scope of theapplication of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to 20 the following detailed description takenin connection with the accompanying drawing, in which:

Fig. 1 is a sectional schematic view of an elemental unilateralconductive couple of the dry surface-contact variety formed inaccordance with the present invention;

Fig. 2 is a sectional view of one structural form of the device of thepresent invention utilizing couples of the type depicted in Fig. 1; a0

Fig. 3 is a sectional view of a structural ymodification on the deviceof the presentl invention;

Fig. 44 is a top plan view with parts in section and parts broken awayof av further structural modification of the device of the presentinven-` tion;

Fig. 5 is an end view of the device depicted in Fig. 4; and

Fig. 6 is a sectional view of one of the couple units of the structuredepicted in Figs. 4 and 5. 40 p Prior to the present invention electriccurrent rectiers and the like which employed asymmetric or unilateralconductive couples of the dry surface-contact variety have been providedwith an essential contact resistance between the elec- 45 tropositiveand electronegative electrode elements in a variety of Ways. Thesedevices, at times, have been characterized by non-uniform operatingcharacteristics, instability during operation under ordinary atmosphericconditions, and have had relatively short .service commercial lives.These and other undesirable characteristics are substantially avoided bythe present invention.

In accordance with the present invention a device of this type isprovided which has anr elecfrom a relatively electronegative materialsuch as a metallic compound or mixture of compounds of elements chosenfrom an empirical group of elements of Sub-group B of the Sixth PeriodicGroup in-Mendelejeffs Periodic Table of Elements, for example, oxides,sulphides, selenides and tellurides. Some of the metallic elements fromwhich it has been found suitable to form these compounds are copper,silver, cadmium, mercury, zirconium, lead, vanadium, arsenic, antimony,tantalum, bismuth, chromium, bolybdenum, tungsten, manganese and iron.Alloys of copper, such as brass, bronze and copper with vany of theelements zinc, silver, lead, tin antimony, etc., have also been foundsuitable from which to form the oxides, sulphides, selenides ortellurides. In addition, mixtures of the compounds, such as mixtures ofoxides of various of the above mentioned metals, mixtures of sulphidesand selenides or tellurides, and mixtures of one or more of suchcompounds with at least one metallic element such as cupric sulphidewith a metal of the chromium group-all have been successfully used aselectronegative electrode materials. The electronegative electrodeelement may consist of a mass of granular electronegative material or asolid body formed-in any suitable and well known manner.

In accordance with one modification of the present invention theelectropositive electrode element is preferably formed from puremagnesium, the surface of which may be oxided in any suitable andwell-known manner. The electronegative electrode element is preferably`formed from a sulphide of copper or an alloy thereof, such as, forexample, brass. This element may be formed in the known manner ofsubjecting a metallic disc to the action of sulphur vapors or a sulphideof the metal may be formed, granulated and pressed into shape.

In accordance with another modification of the present invention, theelectropositive electrode element may be formed from a silicon material,that is, silicon alone or -a compound of silicon and an element chosenfrom an empirical group of more electropositive elements of theelectrochemical table of j elements preferably chosen from the Secondand Third Groups of Mendelejels Periodic Table of Elements, comprisingberyllium, magnesium, calcium, zinc and aluminum. This electropositiveelectrode element is placed in surface contact with an electronegativeelectrode element having a high contact resistance with theelectropositive electrode element and `is preferably formed from, orprovided with, a surface of' a compound of an element chosen from anempirical group of elements of Sub-Group B of the Sixth Periodic Groupin Mendelejeffs Table of Elements, comprising sulphur, selenium andtellurium, or a ymixture of such compounds. The other constituents ofthe compound or compounds forming the electronegative material may be ofany suitable metal or alloy thereof chosen from an empirical group ofmetals or materials comprising copper, silver, brass and bronzes.

The electropositive electrode element is preferably formed from granularmagnesium silicide. The best mesh for such material has been found to bebetween about 36 and 60. With a finer mesh it has been found that thecontact resistance is undesirably high and with a coarser mesh theresultant units are found to be undesirably leaky due to localizedpressure. The electronegative electrode material in many instances isformed from granular cupric sulphide but a more preferable material is amixture of cupric sulphide and cupric selenide of v about mesh. Asuitable method of forming such a mixture is by adding about 20 percentselenium to the cupric sulphide vand then heat treating the mixture fora considerable period of time, for example, about three hours at about250 C. in a vacuum to prevent oxidation and to volatilize any excess ofsulphur and selenium.

With such electropositive and electronegative materials, it is necessaryto use a structure which will confine these granular materialsadjacenteach other with suiiicient pressure to insure good contacttherebetween. This is readily accomplished by using a cup-shaped memberin which the electropositive material in granular form is placed over amass of the electronegative material.

`Any of the above described unilateral conductive couples are improved,in accordance with the present invention, by the use of a substance orsubstances tending to prevent, in operation, the formation of polarizingmaterial adjacent the electronegative material. It has been observed, inthe operation of certain couples, that a rather common progressivedecrease in the output occurs with an attendant decrease in efficiency,which apparently is largely dependent upon the formation of an undesiredlayer of polarizing material adjacent the electronegative material. Byproviding a layer of non-polarizing substance adjacent theelectronegative material in accordance with the present invention, ithas been found that the service life of any greatly increased. 'I'hishaving been determined,

such couples are provided with such a layer of non-polarizing substanceand may be efficiently operated at a substantially constant output for agreatly increased service life. Examples of some of the more desirablenon-polarizing substances are aquadag, nickel, carbonized lead, alloysof nickel and chromium known under the trade name of nichrome", andconductive carbides of relatively low resistance such as tungstencarbide, tantalum carbide and chromium carbide.

A layer of non-polarizing substance is preferably provided in theassembly in the following manner. A carbonized nickel element isinserted adjacent the electro-negative material, preferably in the shapeof a washer. This washer constitutes va sheet of nickel having a coatingof carbon formed thereon. For the carbonized nickel may be substitutedcarbonized lead, that is a lead washer coated with carbon. Such anelement is placed in the assembly with the carbonized side adjacent theelectronegative material. When conductive carbidesI of relatively lowresistance are used, discs are,y formed from pressed powders thereof.Wheat-.alloys of nickel and chromium known under the trade name ofnichrome are carbon, graphite, tin, carbonized a of such couples may beused a nichrome material having a relatively v large amount of chromiumis selected.

It has been found that thin sheets of brass containing about 20 per centor more zinc may be used to prevent the formation of polarizing materialadjacent the electro-negative electrode element provided that therectifier assembly is kept under high pressure and the operatingtemperatures are kept below 150 C. Under such conditions these sheets ofbrass may be considered'to be layers of non-:polarizing material.

Referring to the drawing, Figs. 1 and 2 show structural embodiments ofone form of the device ofthe present invention in which an elementalunilateral conductive couple of the dry surface-contact variety consistsof an electropositive electrode element Il of any suitableelectropositive material, such as, for example, aluminum, magnesium, oran alloy or amalgam thereof, etc. This electrode element is preferablyin the form of a washer and lies in face engagement withthe'electronegative electrode element Il of any suitable electronegativematerial, such as, cupric sulphide, or a sulphided brass body. A layerI2 of non-polarizing substance is placed in contact with the oppositeface of the electronegative electrode element II. When these elementsare in the form of washers they may be readily assembled as depicted inFig. 2. Upon a bolt I3 provided with an insulating collar I4, and a pairof shoulder washers I5 and I6, is mounted a terminal plate I1 in faceengagement with the electropositive electrode element I0 adjacent whichis disposed the electronegative electrode element I I in face engagementwith the layer of non-polarizing substance I2. 'Ihe layer I2 ofnon-polarizing substance engages another terminal plate I8 adjacentwhich is mounted another unilateral conductive couple, thenon-polarizing layer I2 of which engages a third terminal plate I9. Bythe use of a bolt, means are provided for imposing pressure upon theelements to insure eil'lcient contact therebetween.

In Fig. 3 is shown a structural modification preferably used when theelectropositive and electronegative materials are in granular form. Abase member 29, preferably in the shape of a disc or square sheet formedfrom copper, is provided with a threaded shank 2I and a projectingportion 22 serving as a terminal member. On the face of the projectingportion 22 is preferably disposeda washer 23 of lead and a thin sheet ofcarbonized nickel 24. A collar 25 is positioned over the projectingportion 22 to cooperate with the lead washer. 23 and carbonized nickelelement 24 and form a cup member having insulating walls 26 and a bottomprovided with a layer of non-polarizing substance. The collar 25 may beformed from any suitable insulating material such as a vitrous enamel ormagnesium silicate known to the trade as steatite and lavite, but ispreferably formed from aluminum and coated on the inside with aninsulating oxide layer 26.

A mass 21 of granular electronegativematerial, preferably a mixture ofcopper sulphide and copper selenide, particles of which are preferablyof about 100 mesh, is placed in the collar 25 over the layer ofnon-polarizing substance 24. A mass of electropositive material, such asmagnesium silicide in granular form, the particles of which are of asize which will pass through a screen of between about 36 mesh and 60mesh, is positioned over the mass 21 of electronegative material withinthe collar 25. Another lead washer 23 is placed over the electropositivema terial 2l with, if desired, an interposed element 24' of plain nickelyto prevent the grains of electropositive material from biting into -therelatively soft surface of the Alead washer 23 when pressure is applied.Another base member 26', having a threaded shank 2i and a projectingportion 22', serving as the other terminal member, Ais positioned asshown with the face of the projecting portion 22' in contact with thelead washer 23' within the collar 25. A resilient spider 29, having thearms thereof bowed as shown, is positioned over the shank 2l and boltsextending through holes in the arms of the spider 29 and the basemembers 29 and 20 complete the assembly. The bolts 30 are provided withsuitable insulating, collars 3| to prevent short-circuiting of theasymmetric couple. An electrical terminal 32 is mounted upon the basemember 29. The unit may be completed by mounting an additionalelectrical terminal 32 on the unit electrically connected with the basemember 20' or, when these units are desired to be arranged in series, bycoupling together shank ZI' with' the shank 2| of an adjacent unit by aninternally'threaded collar 33.

In Fig. 4 is shown a structural modification of the device depicted inFig. 3 with four unilateral conductive couples arranged to changealternating current to direct current. consists of a pair of basemembers 34 and 34', preferably of copper and provided with plugs orprojecting-portions 35 and 35' adapted to serve as terminal members ofthe couple. Plugs 35 and 35' extend through the base members 34 and 34'respectively to form projections 36 and 36'. Adjacent couples have theirbase members 34', 34' electrically connected together by a metallicsleeve 31 which receives the projections 36', 36' as shown. Each coupleis completed by a unit 38 which includes the electropositive andelectronegative electrode elements, one of which is electricallyconnected to the plug 35 and the other of which is electricallyconnected to plug 35'.

'Ihe couples are preferably mounted in banks of two and secured togetherby bolts 39, 39, passing through end blocks 40, 4D, preferably of steelso'that the couples may be kept under desired pressure. The bolts 39, 39may, if desired, pass through apertures in the base members 34, 34 sincethe latter are preferably made with a large surface area to act asefficient heatdissipating ns. In such case insulating sleeves 4I, 4I aremounted on the bolts 39, 39 to eliminate the possibility of the couplesbeing short-circuited by the bolts 39, 39. 'I'he endsf'blocks 40, 40 areapertured to receive the projections 36, 36 and at least between one endblock 40 and the adjacent base member 34 a shim 42 is mounted to allowthe end block 40 to be resiliently stressed. The base members 34, 34 areprovided with brackets 43, 43 to serve as supports and electricalconnections.

As shown in Fig. 4, two banks are mounted side by side on metallicstrips 44 and 45 which serve as electrical connectors between adjacentbanks.

- The resultant structure is used to change alter nating current todirect current by connecting the alternating current terminals 46 and 41to the metallic strips 44 and 45, the direct current being deliveredfrom the assembly lby direct current terminals 48 and 49, one connectedto avbase member 34' in one bank and the other connected to a basemember 34' in the other bank.

The couple unit 38 depicted in Fig. 6 is generally similar to thatdepicted in Fig. 3. It in- Each couple cludes a. collar 50. ofinsulating material such as magnesium silicate commercially known as"steatite" and lavite surrounded by a metallic ring 5I preferably ofbrass adapted to strengthen the collar 50 and to serve as a heatdssipator. An additional feature of the unit 38 is the provision of awelded junction which increases the operating eilciency, avoids thenecessity of a forming period when the unit is put in operation, andresults in a unitary structure which can be readily handled. f

'I'he welded junction is preferably obtained by placing the collar 50over a projecting electrode and inserting therein a lead washer 23,preierably about mils thick, a carbonized nickel disc 24, preferablyabout one mil thick, a small c amount of electronegative material,preferably a mixture of cupric sulphide and cupric selenide of about 100mesh, a suitable amount of magnesium silicide, preferably between about36 and 60 mesh, a nickel disc 24' and an additional lead washer 23' inthe order set forth. A second electrode is brought into contact with thelead washer 2l',

pressure is applied, and current at a voltage and amperage greater thanthat at which the couple is designed to operate is allowed to flowbetween the electrodes from the electronegative material or anode sideto the electrorespective material or cathode side. This flow of currentis continued until the materials are welded together. As an example,welded junction couples designed to deliver about 5 amperes directcurrent at about 7 volts have been formed by placing them in a directcurrent circuit containing a variable resistance adjusted to allow about50 amperes at about 12 volts to flow through the couple for periods ofabout 2 seconds each, these being repeated until the current flow wasabout 30 amperes. The resistance was then increased until the currentflow was about 18 to 20 amperes and several 5-second periods of flowused until the voltage reached a. maximum. Obviously, however, theproduction of welded junctions is not dependent upon the methoddescribed.

'I'he use of at least one lead washer 23 adjacent the element 2l ofnon-polarizing substance is preferred in the assemblies since whensuilicient pressure is applied to a couple unit the lead washer will beexpanded to close completely the end of the collar 25 or 50 and sealoiit` from the atmosphere the relatively unstable electronegativematerial.` To insure eilicient sealing a second lead washer 23 is usedadjacent the electrcpositive material as shown.

The pressure used in the formation of welded junctions not only insuresgood contact between the electropositive and electronegative materialsto obtain an eflicient weld and formation of a current-blocking film butalso expands the lead Washers to seal oil the electrode materials.

Pressure is additionally used in the completed assemblies to insure goodcontact between the adjacent surfaces of the elements, to allow theeflicient formation at the junctions between the electropositivematerial and the electronegative material of an inverse current-blockinglm when welded junctions are not used, to insure the maintenance of thecurrent-blocking lm during the operation of the device, and to allowrapid dissipation of heat.

In the operation of the device depicted the electropositive materialforms the cathode and the electronegative material forms the anode and,when current is passed between these electween. It is believed, but

practice of the particular 'mass of silicide of magnesium trode elementsduring the forming period, aneinverse current-blocking lm is formedtherebeit is by no means certain that this current-blocking illmwhen theanode is of copper sulphide and the cathode is of magnesium silicide, isa sulphide of 'silicon and magnesium. I do not wish, however, to bebound by this theory with regard to the probable nature of the compoundscomprising the inverse current-blocking nlm.

The use of the non-polarizing substance, such as carbon, apparentlyprevents in operation the formation 61' polarizing materialadjacent thev electronegative material which has been found progressively todecrease the output of the asymmetric or unilateral conductive `couplewith av consequent decrease in efficiency and a relatively short servicelife.

It will thus be seen that the present invention t eiliciently attainsthe objects set forth above and provides asymmetric or unilateralconductive couples which are simple and rugged in structure landelllcient in operation, units including electropositive electrodeelements oi' a silicide oi' magnesium and eiectroneg'ative electrodeelements of an electronegative material including a sulphide of copperwith which is associated a layer of a non-polarizing substance such ascarbon having been operated continuously for periods greater than 1500hours at a current density of about amperes per square inch and 10 voltspotential per couple without any appreciable decrease in the outpu Theuse of the expression non-polarizing substances is intended to cover allsubstances of the type set forth above which have the property inunilateral conductive Vcouples of preventing the formation inoperation-of materials adjacent the electronegative material whichdevelopduring operation and decrease the output of the couple.

Since certain changes may be made in the above construction anddifferent embodiments of the invention could be made without departingfrom the scopey thereof, it is `intended that all matter contained inthe above description or shown in the accompanying drawing shall be in.-terpreted as illustrative and not in a limiting sense. l

` Having described my invention, what I claim ias new and desire tosecure by Letters Patent,

1. In electric current rectiflers and the like, of

relatively electronegative electrode element including a sulphide ofcopper in surface contact with said electropositive electrode, and a`nonpolarizing element of carbonized nickel in contact with saidelectronegative electrode element.

2. A unilateral conductive couple comprising a maintained in contactwith an electronegative material including a sulphide of copper, and alayerof nonpolaiizing substance in contact with said electroneg'ativematerial.

3. A Vunilateral conductive couple comprising a mass of silicide ofmagnesium maintained in contact with a mixture of a sulphide of copperand a selenide of copper, and a non-polarizing element of carbonizednickel in contact with said mixture.

4. In electric current rectiers and the like, oi' the drysurface-contact variety, a unilateral conductive couple comprising arelatively electropositive electrode element formed from one of thematerials beryllium, magnesium, calcium. zinc, aluminum, silicon andsilicide, another electrode element having a surface of a relativelyelectronegative material of a compound of one of the elements sulphur,selenium and tellurium with one of the materials copper and copperalloys in surface-contact with said electropositive electrode and anon-polarizing element of carbonized nickel in contact with saidelectronegative electrode element.

5. In electric current rectiflers and the like of the drysurface-contact variety, a unilateral conductive couple comprising arelatively electropositive electrode element formed from one of thematerials beryllium, magnesium, calcium, zinc, aluminum, silicon andsilicide, another electrode element having a surface of a relativelyelectro- Inegative material of a compound of one of the elementslsulphur, selenium and tellurium with one of the materials copper andcopper alloys in surface contact with said electropositive electrodeadapted to cooperate with the former for the electrochemical formationand maintenance of an inverse current-blocking iilm at theirjunction,`and a layer of non-polarizing carbon containing material incontact with said electronegative material.

6. In electric current rectiers and the like, of the dry surface-contactvariety, a unilateral conductive couple comprising a relativelyelectropositive electrode element formed from one of the materialsberyllium, magnesium, calcium, zinc, aluminum, silicon and silicide,another electrode elementxhaving a surface of a relativelyelectronegative material of a compound of one of the elements sulphur,selenium, and tellurium with one of the materials copper and copper algloys in surface contact with said electropositive electrode adapted tocooperate with the former for the electrochemical formation andmaintenance of an inverse current-blocking lm at their junction, and anon-polarizing element comprising a metal disc having a carbonizedsurface in contact with said electronegative material.

'1. In electric current rectifiers and the like, of

the dry surface-contact Variety. a unilateral conductive couplecomprising a relatively electropositive electrode element formed fromone of the materials beryllium, magnesium, calcium,

zinc, aluminum, silicon and silicide, another electrode element of arelatively electronegative material formed from a compound of -one ofthe elements sulphur, selenium and tellurium with one of the materialscopper and copper alloys, said electronegative body adapted to cooperatewith the electropositive body for the electrochemical formation andmaintenance of an inverse current-blocking nlm at their junction, and anon-polarizing element in contact with said Aelectronegative electrode.said non-polarizing element comprising one of the substances aquadag,carbon, graphite. tin, carbonized nickel, carbonized lead, tungstencarbide, tantalum carbid chromium carbide and alloys of nickel andchromium in which the amount of chromium preponderat. L

8. In electric current rectifiers and the like, of the drysurface-contact variety, a unilateral conductive couple comprising arelatively electrof positive electrode element formed from one of thematerials beryllimn, magnesium. calcium, zinc, aluminum, silicon andsilicide, another electrode element of a relatively electronegativematerial formed from a compound of one of the elements sulphur, seleniumand tellurium with one of the materials copper, brass and bronze, saidelectronegative body adapted to cooperate with the electropositive bodyfor the electrochemical formation and maintenance of aninelectronegative element including a sulphide of copper in surfacecontact with said electropositive electrode and a non-polarizing elementhaving a carbon surface in contact with said electronegative electrodeelement.

SAMUEL RUBEN.

